The subject matter disclosed herein generally relates to gas turbine engines and, more particularly, to adjustable blade outer air seals for gas turbine engines.
Gas turbine engines are design to have minimal clearances between outer edges of turbine blades (blade tips) and inner surfaces of rotor case shrouds, i.e., blade outer air seals. With increased clearance comes more aerodynamic loss (inefficiency) commonly referred to as “tip leakage.” The clearances between the blade tips and the inner surfaces of the blade outer air seals are often oversized to avoid undesirable abrasion (“rubbing”) between these two components. The oversizing clearance gap is undesirable as it represents a loss in overall gas turbine engine cycle efficiency. This is especially pertinent to typical aero-gas turbine engines which operate in a typical open Brayton cycle and have no additional thermodynamic benefits that may be derived from, for example, recuperation, turbo-compounding, combining with other cycles (Rankine, Otto, Diesel, Miller, etc.), etc.
More emphasis of the main propulsion share of a gas turbine engine is shifted to the bypass air flow compared to the core air flow. Therefore, while the bypass fan increases in diameter, the engine's core is shrinking in diameter. Accordingly, all of the internal rotation components of the engine core are being reduced in size. As a result ever tighter internal clearances are desired to optimize the performance of the core of the gas turbine engine. Accordingly it may be desirable to improve optimization of the clearance.